1. Field of the Invention
The present invention relates to a solenoid valve for a brake system, and more particularly, to a solenoid valve for a brake system capable of being more easily manufactured and reducing manufacturing costs.
2. Description of the Related Art
Generally, an anti-lock brake system for vehicles serves to prevent locking of wheels by sensing slippage of the wheels and suitably controlling braking pressure applied to the wheels. The wheels of the vehicle do not slip during braking by means of the anti-lock brake system, whereby the steering performance of the vehicle is maintained, and the vehicle is stopped safely.
In order to control braking pressure, the brake system includes a plurality of solenoid valves to open or close a fluid path of a braking hydraulic pressure line. The solenoid valves include normal open type solenoid valves which are normally kept in an opened state, and normal close type solenoid valves which are normally kept in a closed state.
FIG. 1 shows a conventional normal close type solenoid valve. A conventional normal close type solenoid valve is press-fitted in a bore 14 of a modulator block 13, in which fluid paths of a brake system are formed. The valve includes a hollow valve housing 1 having an inlet 3 and an outlet 4, through which fluid flows.
A cylindrical-shaped sleeve 6 is coupled to an end portion of the valve housing 1, and an armature 5 is slidably mounted in the sleeve 6. A valve core 7 is coupled to an opened end portion of the sleeve 6 to shield the opened end portion of the sleeve 6 and to slide the armature 5. The armature 5 opens or closes an orifice 8a of a valve seat 8 by its sliding motion. To achieve this, the armature 5 is provided with an opening/closing portion 5a which is extended toward the valve seat 8 through a hollow portion 2 of the valve housing 1.
A restoring spring 9 is mounted between the armature 5 and the valve core 7, so as to press the armature 5 to close the orifice 8a in a normal state. An exciting coil assembly 10 is mounted around the sleeve 6 and the valve core 7, so as to slide the armature 5. An orifice member 11 is mounted in the valve housing 1, and an O-ring 12 is mounted on an outer peripheral surface of the valve housing 1 to form a seal between the valve housing 1 and an inner surface of the bore 14.
When electric power is applied to the exciting coil assembly 10, the armature 5 is moved toward the valve core 7 by a magnetic force, and opens the orifice 8a of the valve seat 8. When electric power is not applied to the exciting coil assembly 10, a magnetic force is not generated, and the armature 5 is moved to close the orifice 8a by an elastic force of the restoring spring 9.
As described above, the conventional solenoid valve is constituted such that the valve housing and the valve seat are separately provided, the valve seat is press-fitted in the valve housing, and the opening/closing portion of the armature is extended toward the valve seat through the hollow portion of the valve housing. However, the conventional solenoid valve as constituted above has problems such that the opening/closing portion of the armature should be formed long, the number of components is large, the structure is complicated, and the valve's manufacturing is difficult. Accordingly, manufacturing costs are high.
Further, because the sleeve and the valve core are coupled to each other through a welding process, and also the sleeve and the valve housing are coupled to each other through a welding process, the above-described conventional solenoid valve has shortcomings of high work effort and low assembling productivity.